Analog noise is subtracted from an optical communication channel using stable, non-absorbing optical hard limiters. A reference signal B is combined with a control signal of intensity I2 through a 3 dB optical coupler to form a first combined signal having an intensity substantially equal to (B/2I1)....http://www.google.de/patents/US6516106?utm_source=gb-gplus-sharePatent US6516106 - Subtracting analog noise from an optical communication channel using stable, non-absorbing optical hard limiters
